Project Summary/Abstract Music learning that starts early in development has profound and long-lasting benefits later in life, within and beyond the music domain, in important areas such as speech and language skills, cognitive skills and social/emotional skills. Previously, work by the PI demonstrated that a short-term music intervention at as early as 9 months of age, during the ?sensitive period? for speech learning, can already affect cortical processing beyond music. That is, infant who underwent the music intervention also exhibited enhanced cortical processing of nonnative speech compared to the controls who underwent free play sessions. The proposed project aims to expand on these results and investigate the extent of the effects from the music intervention in infancy, more specifically, whether the music intervention can already modulate speech encoding at the lower level auditory brainstem. Understanding this question is critical from a theoretical and an application perspective. Theoretically, the results will improve the basic scientific understanding of mechanisms underlying the effects related to music intervention and its interaction with early development and speech learning. In practice, the knowledge we gain from the basic research will help future implementation of early music intervention programs as an alternative method to improve early speech and later language learning, for typically developing infants and more importantly, for infants at-risk for speech and language disorders. The first study (Aim 1) will measure infants? brainstem encoding of nonnative lexical tones at 7 months and 11 months of age. The results from this group will serve as controls for Aim 2. At the same time, the results from Aim 1 will also establish the typical developmental trajectory for brainstem encoding of lexical tones, which has not been established before. The results will thus also expand our current understanding of behavioral and neural changes that take place during the ?sensitive period? for phonetic learning. In the second study (Aim 2), infants will complete the previously-established music intervention starting at 9 months of age, in addition to the brainstem measurements at 7 and 11 months of age. Their results will be compared to the controls (Aim 1) to address the effects related to the music intervention. Together, the proposed study will further our understanding of the effect related to music intervention in infancy and its underlying mechanisms. This project will also help the PI to take a big step towards her long-term goal to apply early music intervention to help infants at-risk for communication disorders.